Waking up to dripping windows is a common problem in UK homes, especially during winter. Condensation on windows isn't just annoying — it can lead to black mould, peeling paint, and even structural damage if left untreated. This guide explains why condensation happens and how to stop it.

What is condensation? Condensation forms when warm, moist air hits a cold surface (like a window). The air cools rapidly and releases water droplets on the glass.

What Causes Condensation on Windows?

Everyday activities produce surprising amounts of moisture:

  • Breathing: A family of 4 produces 2-3 litres of moisture overnight
  • Cooking: A single meal can release 2-3 litres of steam
  • Showering/Bathing: Produces 1-2 litres of moisture
  • Drying laundry indoors: Releases up to 5 litres of water
  • Boiling a kettle: Releases steam directly into the air
  • Houseplants: Release moisture through transpiration

How to Remove Condensation Immediately

1

Wipe It Away

Use a clean, dry microfiber cloth or a window vacuum to wipe away condensation as soon as you see it. Leaving moisture on window frames can lead to mould and damage.

2

Open Windows

Create cross-ventilation by opening windows on opposite sides of your home. Even 10-15 minutes a day can dramatically reduce indoor humidity.

Pro Tip: Leave windows on the latch when you're out — it provides continuous ventilation without compromising security.
3

Use Extract Fans

Run extractor fans during and for 20-30 minutes after cooking and showering. Make sure they're clean and working properly — clogged fans are ineffective.

Long-Term Solutions to Stop Condensation

Improve Ventilation

  • Install trickle vents: These small openings in window frames allow constant airflow without losing much heat
  • Use positive input ventilation (PIV): A small unit in the loft pushes fresh, filtered air into your home, pressurising it and pushing moist air out
  • Install a heat recovery ventilator (MVHR): The most effective but most expensive option — extracts moist air while recovering heat

Reduce Moisture Production

  • Cover pans when cooking: Reduces steam by up to 80%
  • Dry laundry outside or in a vented dryer: Never dry clothes on radiators indoors
  • Keep bathroom doors closed when showering: Contains moisture before it spreads through the house
  • Use a dehumidifier: Especially useful in winter when you can't open windows

Upgrade Your Windows

  • Double or triple glazing: The inner pane stays warmer, reducing condensation
  • Secondary glazing: A more affordable retrofit option
  • Thermal blinds/curtains: Keep window glass warmer by trapping a layer of air
Pro Tip: Condensation inside double glazing indicates broken seals. The window needs replacement or repair — DIY methods won't fix it.

Cleaning Mould Caused by Condensation

1

Use White Vinegar

Spray undiluted white vinegar onto mouldy areas. Let it sit for 1 hour, then wipe clean. Vinegar kills mould spores and prevents regrowth.

2

Use Bleach for Tough Mould

Mix 1 part bleach with 4 parts water. Apply, let sit for 10 minutes, scrub with a brush, then rinse. Wear gloves and ventilate the area.

Never mix bleach and vinegar! The combination creates toxic chlorine gas.
3

Repaint with Mould-Resistant Paint

After cleaning, repaint window frames and surrounding walls with mould-resistant bathroom paint to prevent future growth.

Condensation Inside vs Outside Windows

  • Outside condensation: Normal in autumn and spring — caused by temperature differences. No action needed.
  • Inside condensation: Problematic — indicates high indoor humidity. Take action using the methods above.
  • Between panes (double glazing): Broken seal — window needs replacement.
Health warning: Persistent condensation leads to black mould, which can cause respiratory problems, allergies, and asthma attacks. Children, elderly, and those with existing conditions are most at risk.

Quick Condensation Prevention Checklist

  • Wipe windows dry every morning
  • Ventilate for 10-15 minutes daily
  • Use extractor fans when cooking/showering
  • Cover pans while cooking
  • Dry laundry outside or in vented dryer
  • Keep bathroom door closed when showering
  • Maintain a consistent indoor temperature
  • Use a dehumidifier in problem rooms
Ideal humidity levels: Aim for 40-60% relative humidity. Below 30% is too dry (causes respiratory irritation), above 60% causes condensation and mould.